134 lines
2.9 KiB
C
134 lines
2.9 KiB
C
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Per-thread (in Go, per-M) malloc cache for small objects.
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//
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// See malloc.h for an overview.
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#include "runtime.h"
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#include "malloc.h"
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void*
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runtime_MCache_Alloc(MCache *c, int32 sizeclass, uintptr size, int32 zeroed)
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{
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MCacheList *l;
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MLink *first, *v;
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int32 n;
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// Allocate from list.
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l = &c->list[sizeclass];
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if(l->list == nil) {
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// Replenish using central lists.
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n = runtime_MCentral_AllocList(&runtime_mheap.central[sizeclass],
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runtime_class_to_transfercount[sizeclass], &first);
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if(n == 0)
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runtime_throw("out of memory");
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l->list = first;
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l->nlist = n;
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c->size += n*size;
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}
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v = l->list;
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l->list = v->next;
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l->nlist--;
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if(l->nlist < l->nlistmin)
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l->nlistmin = l->nlist;
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c->size -= size;
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// v is zeroed except for the link pointer
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// that we used above; zero that.
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v->next = nil;
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if(zeroed) {
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// block is zeroed iff second word is zero ...
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if(size > sizeof(uintptr) && ((uintptr*)v)[1] != 0)
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runtime_memclr((byte*)v, size);
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else {
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// ... except for the link pointer
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// that we used above; zero that.
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v->next = nil;
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}
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}
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c->local_alloc += size;
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c->local_objects++;
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return v;
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}
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// Take n elements off l and return them to the central free list.
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static void
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ReleaseN(MCache *c, MCacheList *l, int32 n, int32 sizeclass)
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{
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MLink *first, **lp;
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int32 i;
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// Cut off first n elements.
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first = l->list;
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lp = &l->list;
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for(i=0; i<n; i++)
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lp = &(*lp)->next;
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l->list = *lp;
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*lp = nil;
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l->nlist -= n;
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if(l->nlist < l->nlistmin)
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l->nlistmin = l->nlist;
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c->size -= n*runtime_class_to_size[sizeclass];
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// Return them to central free list.
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runtime_MCentral_FreeList(&runtime_mheap.central[sizeclass], n, first);
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}
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void
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runtime_MCache_Free(MCache *c, void *v, int32 sizeclass, uintptr size)
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{
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int32 i, n;
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MCacheList *l;
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MLink *p;
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// Put back on list.
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l = &c->list[sizeclass];
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p = v;
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p->next = l->list;
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l->list = p;
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l->nlist++;
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c->size += size;
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c->local_alloc -= size;
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c->local_objects--;
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if(l->nlist >= MaxMCacheListLen) {
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// Release a chunk back.
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ReleaseN(c, l, runtime_class_to_transfercount[sizeclass], sizeclass);
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}
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if(c->size >= MaxMCacheSize) {
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// Scavenge.
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for(i=0; i<NumSizeClasses; i++) {
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l = &c->list[i];
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n = l->nlistmin;
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// n is the minimum number of elements we've seen on
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// the list since the last scavenge. If n > 0, it means that
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// we could have gotten by with n fewer elements
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// without needing to consult the central free list.
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// Move toward that situation by releasing n/2 of them.
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if(n > 0) {
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if(n > 1)
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n /= 2;
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ReleaseN(c, l, n, i);
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}
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l->nlistmin = l->nlist;
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}
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}
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}
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void
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runtime_MCache_ReleaseAll(MCache *c)
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{
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int32 i;
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MCacheList *l;
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for(i=0; i<NumSizeClasses; i++) {
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l = &c->list[i];
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ReleaseN(c, l, l->nlist, i);
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l->nlistmin = 0;
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}
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}
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